Hermeus unveils assembly of Quarterhorse Mk 2 supersonic jet

Hermeus has reached a new stage in its high-speed aircraft initiative, with the Quarterhorse Mk 2 prototype now structurally assembled and supported by its tricycle landing gear. The startup company shared images confirming the airframe’s mounting as it prepares for the integration of the Pratt & Whitney F100 turbofan engine at its Atlanta facility.

Quarterhorse Mk 2 represents the company’s first platform capable of supersonic flight, following the Mk 1’s maiden flight in May 2025, which focused on validating aircraft design and performance models. The Mk 2 introduces a delta wing configuration and a variable nose-mounted air intake, distinguishing it from its predecessor.

Unlike the planned Mk 3, which aims to exceed Mach 5 and incorporate the Chimera turbine-based combined cycle (TBCC) propulsion system, the Mk 2 uses a modified version of the well-know F100 engine. The key innovation for this stage is a proprietary pre-cooling system, designed to allow the turbojet to operate efficiently at higher speeds by reducing inlet air temperature.

Hermeus’ step-by-step development approach involves using each prototype to validate critical technologies before advancing to hypersonic speeds. The Mk 2 will be essential for testing and refining the pre-cooling system, which is seen as a prerequisite before integrating the scramjet-based TBCC engine in future models.

The Quarterhorse program is structured around an annual cycle of developing and testing new aircraft, with each iteration building on data and outcomes from the previous model. The Mk 1 went from concept to flight readiness in just over a year, though its first flight took place later than initially projected.

Hermeus ultimately intends for the Mk 3 to surpass the 1976 speed record set by the SR-71 Blackbird, which reached 3,529 km/h (Mach 3.3). The company is positioning the Quarterhorse series as a potential technological benchmark in the pursuit of hypersonic flight for the aviation industry.

The first flight of the Quarterhorse Mk 2 is scheduled for later this year, with the platform set to provide data on supersonic operations and validate the pre-cooling technology ahead of the Mk 3’s development.

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Ricardo Meier

Creator of the website that started in 1996 as a magazine. He also writes on Brazilian websites AUTOO, MOTOO and MetrôCPTM.

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